Thermodynamics

1.    An insulated rigid vessel contains a mixture of fuel and air. The mixture is ignited by a minute spark. The contents of the vessel experience

    1) increase in temperature, pressure and energy

    2) decrease in temperature, pressure and energy

    3) increase in temperature and pressure but no change in energy

    4) increase in temperature and pressure but decrease in energy

2.    The specific heat of an ideal gas depends on its

    1) temperature    2) pressure

    3) volume

    4) molecular weight and structure

3.    An isolated thermodynamic system executes a process. Choose the correct statement(s) from the following

    a) No heat is transferred

    b) No work is done

    c) No mass flow across the boundary of the system

    d) No chemical reaction takes place from the system

    1) only a        2) a, b

    3) a, b, c        4) a, b, c, d

4.    If a closed system is undergoing an irreversible process, the entropy of the system

    1) must increase

    2) always remains constant

    3) must decrease

    4) can increase, decrease or remain constant

5.    Heat and work are

    1) intensive properties

    2) extensive properties

    3) point functions    4) path functions

6.    A steel ball of mass 1 Kg of specific heat 0.4KJ/Kg is at a temperature of 600C. It is dropped into 1Kg water at 200C. The final steady temperature of water is

    1) 23.50C        2) 300C

    3) 350C        4) 400C

7.    A gas contained in a cylinder is compressed, the work required for compression being 5000KJ. During the process, the heat interaction of 2000KJ causes the surroundings to be heated. The changes in internal energy of a gas during the process is

    1) -7000KJ    2) -3000KJ

    3) +3000KJ    4) +7000KJ

8.    Which of the following relationships is valid only for reversible processes undergone by a closed system of simple compressible substance (neglect changes in kinetic and potential energy)

    1) dQ = dU + dW    2) TdS = dU + pdv

    3) Tds = dU + dW    4) dQ = dU + pdv

9.    A frictionless piston - cylinder device contains a gas initially at 0.8MPa and 0.015m3. It expands quasistatically at constant temperature to a final volume of 0.030m3. The work output(in KJ) during this process will be

    1) 8.32    2) 12.00  3) 554.67    4) 8320.00

10.    The contents of a well insulated tank are heated by a resistar of 23W in which 10A current is flowing. Consider the tank along with its contents as a thermodynamic system. The work done by the system and heat transfer to the system are positive. The rates of heat(Q), work(W) and change in internal energy(DU) during the process (KW) are

    1) Q = 0; W = -2.3; DU = +2.3

    2) Q = +2.3; W = 0; DU = +2.3

    3) Q = -2.3; W = 0; DU = -2.3

    4) Q = 0; W = +2.3; DU = -2.3

11.    A condensor of a refrigiration system rejects heat at a rate of 120KW, while is compressor consumes a power of 30KW. The coefficient of performance of a system would be

    1) 1/4    2) 4    3) 1/3    4) 3

12.    For an ideal gas the expression





    is always equals to

    1) zero    2) Cp/Cv    3) R    4) RT

13.    One kilogram of water at room temperature is brought into contact with a high temperature thermal reservoir. The entropy change of the universe is

    1) equal to entropy change of the reservoir

    2) equal to entropy change of water

    3) equal to zero    4) always positive

14.    A carnot engine(CE-1) works between two temperature reservoirs A and B where TA= 900K and TB = 500K. A second carnot engine(CE-2) works between temperature reservoirs B and C, where TC = 300K. In each cycle of CE-1 to reservoir B is used by CE-2, For one cycle of operation, if the net Q is absorbed by CE-1 from reservoir A is 150MJ, the net heat rejected to reservoir C by CE-2(in MJ) is

    1) 82.33MJ    2) 83.333MJ

    3) 84.1MJ    4) 85.2MJ

15.    During the phase change of a pure substance

    1) dG = 0        2) dP = 0

    3) dH = 0        4) dU= 0

16.    When wet stream flows through a throttle valve and remains wet at exit

    1) its temperature and quality increase

    2) its temperature decreases but quality increases

    3) its temperature increases but quality decreases

    4) its temperature and quality decreases

17.    2 moles of oxygen are mixed adiabatically with another 2 moles of oxygen in a mixing chamber, so that the final total pressure and temperature of a mixtures become same as those of the individual constituents at their initial status. The change in entropy due to mixing per mole of oxygen is given by

    1) -R ln2        2) 0

    3) R ln2        4) R ln4

18.    A rigid container of volume 0.5m3 contains 1.0Kg of water at 1200C (Vf = 0.00106m3/Kg, Vg=0.8908m3/Kg). The state of water is

    1) compressed liquid    2) saturated liquid

    3) a mixture of saturated liquid and saturated vapour

    4) super heated vapour

19.    For a given set of operating pressure limits of a rankine cycle the highest efficiency occurs for

    1) saturated cycle    2) super heated cycle

    3) reheat cycle    4) regenerative cycle

20.    Which amount of following is the boiler mounting?

    1) Blow off clock    2) Feed pump

    3) Economizer    4) Super heater

21.    Which of the following is a pressure compounded turbine

    1) Parsons    2) Curtis

    3) Rateau        4) All

22.    In a power plant, water (density =

    1000 Kg/m3) is pumped from 80KPa to 3MPa. The pump has an isentropic efficiency of 0.85. Assuming that the temperature of the water remains the same, specific work(in KJ/Kg) supplied to the pump is

    1) 0.34    2) 2.48    3) 2.92    4) 3.43

23.    A cycle consisting of two reversible isothermal processes and two reversible isobaric processes is known as

    1) Atkinson cycle    2) Stirling cycle

    3) Brayton cycle    4) Ericson cycle

24.    With increasing temperature of intake air, CI engine efficiency

    1) decreases    2) increases

    3) remains same

    4) depends on other factors

25.    For a spark ignition engine, the equivalence ratio(f) of mixture entering the combustion chamber has values

    1) f <1 for idling and f >1 for peak power conditions

    2) f >1 for both idling and peak power conditions

    3) f >1 for idling and f <1 for peak power conditions

    4) f <1 for both idling and peak power conditions

26.    A cylinder contains 5m3 of an ideal gas at a pressure of 1 bar. This gas is compressed in a reversible isothermal process till its pressure increases to 5 bar. The work in KJ required for this process is

    1) 804.7        2) 953.2

    3) 981.7        4) 1012.2

27.    A gas turbine cycle with infinitely large number of stages during compression and expansion leads to

    1) Stirling cycle    2) Atkinson cycle

    3) Ericsson cycle    4) Brayton cycle

28.    For a single stage impulse turbine with rotor diameter of 2m and a speed of 3000rpm when the nozzle angle is 200, the optimum velocity of steam in m/s is

    1) 334    2) 356    3) 668    4) 711

29.    At a triple point of a pure substance, the number of degrees of freedom is

    1) 0    2) 1    3) 2    4) 3

30.    Considering the variations of static pressure and absolute velocity in an impulse steam turbine, across one row of moving blades

    1) both pressure and velocity decreases

    2) pressure decreases but velocity increases

    3) pressure remains constant, while velocity increases

    4) pressure remains constant, while velocity decreases.



Answers



1)  3    2) 4    3) 3    4) 4    5) 4

6) 1    7) 3    8) 4    9) 1    10) 1

11) 4    12) 3    13) 4    14) 2    15) 1

16) 2    17) 2    18) 3    19) 4    20) 1

21) 3    22) 4    23) 4    24) 4    25) 2

26) 1    27) 3    28) 3    29) 1    30) 4